Broad-band injected-beam crossed-field amplifiers

The design and operation of injected-beam-crossed-field amplifiers, which provide efficient amplification over octave frequency bands with grid control in compact PM Focused format, are described. Dielectric supported meander lines, which are used to provide the low-dispersion and high-interaction impedance required to achieve octave bandwidth, are detailed. Relationships between space charge, gain factor, beam impedance, circuit loss, and circuit dimensions are derived for design optimization. An electron gun with a negative grid, which provides noise suppression, as well as a nonintercepting current control electrode, is shown to be effective in controlling the beam current continuously from zero to full operating value. Operating characteristics of production CFA's, providing 1 kW of average power in pulsed and CW operation and up to 5-kW peak pulsed power, are presented to illustrate the inherent multimode performance which can be achieved with low-voltage grid control.